dovecot - Apr 2014 - POP3: Panic: Trying to allocate 0 bytes

Hi,

today I upgraded one of our dovecot servers from 2.117 to version 2.2.12 under
Debian Squeeze.
After the upgrade I got many of the following errors for pop3 users.

My logfile shows:

...
Apr 14 09:28:05 mailstore dovecot: pop3(user at domain.net pid:39688
session:<o1DTn/v2IABPNmv7>): Panic: Trying to allocate 0 bytes
Apr 14 09:28:05 mailstore dovecot: pop3(user at domain.net pid:39688
session:<o1DTn/v2IABPNmv7>): Error: Raw backtrace:
/usr/lib/dovecot/libdovecot.so.0(+0x6bb0a) [0x7f1ae9a18b0a] ->
/usr/lib/dovecot/libdovecot.
so.0(+0x6bb86) [0x7f1ae9a18b86] ->
/usr/lib/dovecot/libdovecot.so.0(i_error+0) [0x7f1ae99d1e8f] ->
/usr/lib/dovecot/libdovecot.so.0(+0x8148b)
[0x7f1ae9a2e48b] -> dovecot/pop3() [0x4077f0] ->
dovecot/pop3(client_command_execute+0x9d) [0x4
07d0d] -> dovecot/pop3(client_handle_input+0x80) [0x405810] ->
/usr/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x4e) [0x7f1ae9a28d2e] ->
/usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0xaf)
[0x7f1ae9a29e9f] -> /usr/lib/do
vecot/libdovecot.so.0(io_loop_handler_run+0x9) [0x7f1ae9a28db9] ->
/usr/lib/dovecot/libdovecot.so.0(io_loop_run+0x38) [0x7f1ae9a28e38] ->
/usr/lib/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f1ae99d6c43] ->
dovecot/pop3(main+0x2
57) [0x404a67] -> /lib/libc.so.6(__libc_start_main+0xfd) [0x7f1ae9669c8d]
-> dovecot/pop3() [0x4045b9]
Apr 14 09:28:05 mailstore dovecot: pop3(user at domain.net pid:39688
session:<o1DTn/v2IABPNmv7>): Fatal: master: service(pop3): child 39688
killed with
signal 6 (core dumps disabled)

....


Have you any idea what the error could be?
As this is a production server I switched back to version 2.1.17.

Many thanks
Urban Loesch

doveconf -n:
# 2.2.12 (978871ca81e7): /etc/dovecot/dovecot.conf
# OS: Linux 3.4.67-vs2.3.3.9-rol-em64t-efigpt x86_64 Debian 6.0.9 ext4
auth_cache_negative_ttl = 0
auth_cache_size = 40 M
auth_cache_ttl = 1 weeks
auth_mechanisms = plain login
auth_verbose = yes
deliver_log_format = msgid=%m: %$ %p %w
disable_plaintext_auth = no
login_trusted_networks = $INTERNAL_IPS
mail_gid = mailstore
mail_location = mdbox:/home/vmail/%d/%n:INDEX=/home/dovecotindex/%d/%n
mail_log_prefix = "%s(%u pid:%p session:<%{session}>): "
mail_plugins = " quota mail_log notify zlib"
mail_uid = mailstore
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character
vacation subaddress comparator-i;ascii-numeric relational regex imap4flags
copy include variables body enotify environment mailbox date ihave imapflags
notify
mdbox_rotate_size = 10 M
namespace inbox {
  inbox = yes
  location   mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Items" {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix   separator = /
  type = private
}
passdb {
  args = /etc/dovecot/dovecot-sql-account.conf
  driver = sql
}
plugin {
  mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename
  mail_log_fields = uid box msgid size from
  mail_log_group_events = no
  quota = dict:Storage used::file:%h/dovecot-quota
  quota_rule2 = Trash:storage=+100M
  quota_warning = storage=95%% quota-warning 95 %u
  quota_warning2 = storage=80%% quota-warning 80 %u
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
  sieve_extensions = +notify +imapflags
  sieve_max_redirects = 10
  zlib_save = gz
  zlib_save_level = 9
}
protocols = imap pop3 lmtp sieve
service auth {
  unix_listener auth-userdb {
    group = mailstore
    mode = 0660
    user = root
  }
}
service imap-login {
  inet_listener imap {
    port = 143
  }
  process_limit = 256
  process_min_avail = 25
  service_count = 1
}
service imap {
  process_limit = 256
  process_min_avail = 25
  service_count = 1
}
service lmtp {
  inet_listener lmtp {
    address = *
    port = 24
  }
  unix_listener /var/spool/postfix/private/dovecot-lmtp {
    group = postfix
    mode = 0666
    user = postfix
  }
}
service pop3-login {
  inet_listener pop3 {
    port = 110
  }
  process_limit = 256
  process_min_avail = 25
  service_count = 1
}
service pop3 {
  process_limit = 256
  process_min_avail = 25
  service_count = 1
}
service quota-warning {
  executable = script /usr/local/rol/dovecot/quota-warning.sh
  unix_listener quota-warning {
    user = mailstore
  }
  user = mailstore
}
ssl = no
ssl_cert = </etc/dovecot/certs/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.pem
userdb {
  args = /etc/dovecot/dovecot-sql-account.conf
  driver = sql
}
protocol lmtp {
  mail_fsync = optimized
  mail_plugins = " quota mail_log notify zlib sieve zlib"
}
protocol imap {
  imap_client_workarounds = tb-extra-mailbox-sep
  imap_id_log = *
  imap_logout_format = bytes=%i/%o session=<%{session}>
  mail_max_userip_connections = 40
  mail_plugins = " quota mail_log notify zlib imap_quota imap_zlib"
}
protocol pop3 {
  mail_plugins = " quota mail_log notify zlib"
  pop3_logout_format = bytes_sent=%o top=%t/%p, retr=%r/%b, del=%d/%m, size=%s
uidl_hash=%u session=<%{session}>
  pop3_reuse_xuidl = yes
}